IMS / Core Test Engineer

Qualitest; Greater London; On-site; GBP 39,000 - 79,000; Full time

Job summary

Qualitest is seeking an experienced IMS / Core Test Engineer to support the validation and testing of mobile network core and IMS services for a leading telecommunications client. The role is based in Bristol with on-site attendance required three times weekly, focusing on ensuring quality, performance, and reliability of voice, messaging and data services.

You will collaborate with network engineering, development, operations and vendor teams to validate roaming, mobility management and

Qualifications

• Experience working within telecommunications testing environments.
• Strong understanding of IMS architecture and protocols.
• Hands-on experience testing VoLTE, VoWiFi, SIP, Diameter, RTP, and related technologies.
• Knowledge of EPC and/or 5G Core network components and interfaces.
• Experience using network analysis tools such as Wireshark, QXDM, or similar.
• Ability to analyse signalling traces and troubleshoot end-to-end service issues.
• Experience working with defect management and test management tools.
• Understanding of mobile network architecture including LTE and 5G technologies.

Responsibilities

• Design, develop, execute, and maintain test cases for IMS and Core Network platforms.
• Perform end-to-end testing of VoLTE, VoWiFi, SMS, MMS, data services, and supplementary services.
• Validate IMS call flows, SIP signalling, Diameter interfaces, and network interoperability.
• Execute functional, integration, regression, system, and user acceptance testing activities.
• Analyse network traces and logs to identify root causes of defects and performance issues.
• Support testing across EPC and 5G Core network elements including MME, HSS, PCRF, AMF, SMF, UDM, and PCF.
• Validate roaming, emergency calling, handover, and mobility management scenarios.
• Collaborate with vendors and internal stakeholders to investigate and resolve defects.
• Create detailed test reports, defect documentation, and release readiness assessments.
• Support automation initiatives where applicable to improve testing efficiency and coverage.
• Participate in release planning, risk assessment, and production deployment activities.

Skills

IMS testing

VoLTE

VoWiFi

SIP

Diameter

5G Core

EPC

Network tracing

Tools

Wireshark

QXDM

Job description

Salary: £39,000 - 79,000 per year

Requirements:

• Experience working within telecommunications testing environments.
• Strong understanding of IMS architecture and protocols.
• Hands-on experience testing VoLTE, VoWiFi, SIP, Diameter, RTP, and related technologies.
• Knowledge of EPC and/or 5G Core network components and interfaces.
• Experience using network analysis tools such as Wireshark, QXDM, or similar.
• Ability to analyse signalling traces and troubleshoot end-to-end service issues.
• Experience working with defect management and test management tools.
• Understanding of mobile network architecture including LTE and 5G technologies.
• Strong analytical, troubleshooting, and communication skills.

Responsibilities:

• Design, develop, execute, and maintain test cases for IMS and Core Network platforms.
• Perform end-to-end testing of VoLTE, VoWiFi, SMS, MMS, data services, and supplementary services.
• Validate IMS call flows, SIP signalling, Diameter interfaces, and network interoperability.
• Execute functional, integration, regression, system, and user acceptance testing activities.
• Analyse network traces and logs to identify root causes of defects and performance issues.
• Support testing across EPC and 5G Core network elements including MME, HSS, PCRF, AMF, SMF, UDM, and PCF.
• Validate roaming, emergency calling, handover, and mobility management scenarios.
• Collaborate with vendors and internal stakeholders to investigate and resolve defects.
• Create detailed test reports, defect documentation, and release readiness assessments.
• Support automation initiatives where applicable to improve testing efficiency and coverage.
• Participate in release planning, risk assessment, and production deployment activities.

Technologies:

• Support
• Mobile
• Network

More:

Qualitest is seeking an experienced IMS / Core Test Engineer to support the validation and testing of mobile network core and IMS services for a leading telecommunications client. We are looking for someone to help ensure the quality, performance, and reliability of voice, messaging, data, and next-generation communication services across complex telecom environments. You will work closely with network engineering, development, operations, and vendor teams across IMS, EPC/5GC, VoLTE, VoWiFi, and related domains, supporting both new feature delivery and production assurance initiatives. The role is located in Bristol, with on-site attendance required three times a week.

last updated 36 week of 2026